Magnetron



Febo ll, 1947.

\ fg) .17?15 gf M54? A H. B. 'DE VORE MAGNETRON Filed April 21, 1943 2sheets-sheet 1f' INVENTOR HENRY 5D @Voka- MAGNETRN 2 Sheets-Sheet 2 KFiled April 21, 194:5

INVENTOR HENRY BDI-:Vomiwwf ATTORNEY Patented Feb. 11, 1947 MAGNETRONHenry B. De Vore, Grovers Mill, N. J., assignor to Radio Corporation ofAmerica, a corporation of Delaware Application April 21, 1943, SerialNo. 483,848

(Cl. 25o-27.5)

13 Claims.

' My invention relates to electron discharge devices suitable for use atultra high frequencies, particularly to such devices of the magnetrontype.

Magnetrons of the split-anode type represent one of the most convenientmeans for generation of ultra high frequency oscillations. In this formof tube an elongated cathode is surrounded by two anode segments whichare connected together through a resonant circuit. A magnetic field isapplied nearly parallel to the cathode and between the cathode and anodesegments. The angle between the cathode and field may be a few degrees;for example, three to six degrees has been found to be effective. Whenthe two anode segments are connected together through a resonantcircuit, this presents a severe limitation in the size of the anodesegments, and hence in the power which may be dissipated when such atube is designed to generate `oscillations above about 10,000 megacyclesfrequency. For, in order that the capacitance between the anode segmentsbe made small enough to form a circuit resonant of these frequencies,the segments must be made very small.

An object of my invention is to provide an electron discharge deviceparticularly useful at ultra high frequencies.

More particularly it is an object of my invention to provide such adevice of the magnetron type capable of large power outputs.

A still further object of my invention is to provide a magnetron whichis particularly suitable for ultra high frequency oscillation but inwhich nevertheless the electrode elements are relatively large so thatthe heat dissipating surfaces permit a large power input to the tube andhence a large power output, the large size of the electrodes permittingsimplification of construction. The novel features which I believe tobecharacteristic of my invention are set forth with par- Vticularty inthe appended claims, but the invention itself will best be understood byreference to the following description taken in connection with theaccompanying drawing in which Figure 1 is a partial longitudinal sectionof one form of 'electron discharge device made according to myinvent-ion, Figure 2 is a, longitudinal section taken 90 to Figure 1,Figure 3 is a schematic diagram showing the voltage distribution duringoperation 'of a device made according to my invention, Figure 4 is aschematic diagram of an electron discharge device made according to myinvention and associated voltage sources, Figure 5 shows a longitudinalview partially in section of a modification of the device shown inFigure 1, and Figure 6 is a longitudinal view partially in section andtaken with respect to Figure 5.

Referring to Figure 1, an electron discharge device made according to myinvention includes an evacuated envelope I0 provided with a press II andthe usual base I2 and pinsl I3. The electrode mount assembly includes alamentary type cath.- ode I4 connected to and supported by thecathodeleads and supports I5 and I6, which in turn are supported by the glassbead members I1 and I8, the cathode leads I9 and "20 being extendedthrough the press. A conventional getter 2I may be supported by the lead20. Shields 22 and 23 are supported on the Acathode leads for protectingthe glass beads II and I8 from metal evaporation and deposition from theelectrode assemb1y.

According to my invention the anode is in the form of a, resonant cavitycircuit or resonator resonant to electromagnetic radiation oroscillation at the frequency to be generated.

The anode elements are incorporated in the walls of resonant cavitycircuit or resonator 23 through which the cathode I4 extends. Thisresonator comprises a pair of coaxial coextensive tubular members 24 and25 closed at the top andA bottom ends by means of the annular shapedmembers 26 and 21. The transverse section of the resonator parallel tothe longitudinal axis of the tube is an annulus, and the space enclosedis of annular shape.

This resonator is supported from the press by means of the lead andsupport wires 28 and 29 and by means of a cross member 3f) secured toelement 3l and cross member 32 secured to element 33. l

A coupling loop 34 extends within the resonator 180 removed from thecathode and is merged into a coaxial line, the outer conductor 35 ofwhich extends into the tubular extension IIJ' of the envelope. Thiscoaxial line is supported by means of the elements 36 and 31. The end ofthe inner conductor 35 preferably extends 3A of a wavelength beyond theend of conductor 35 and serves as a radiator and may be coupled to awave guide. Other coupling means could be used, of course, such asprobes'or apertures opening into wave guides.

The magnetic field for bringing about magnetron operation is provided bymeans of the magnets 31 and 38 mounted on opposite sides of theresonator so that the magnetic eld is produced between the cathode andthe walls of the resonator, and preferably nearly'parallel to thecathode. The walls 24 and 25 of the resonator 3 serve as the anodes ofthe magnetron. The cathode is positioned to emit and direct electronsinto a region of the resonator in which the oscillating electric iieldcan exist.

As shown in Figure 4, the cathode is supplied by means of the battery55, and the voltage on the resonator and anode by means of the voltagesource 58. The voltage distribution in an oscillating electromagneticfield within the resonator during operation is shown in Figure 3, themagnitude of the voltage E being represented by the radially directedarrows. Maximum voltage diiferential in the form of a standing waveoccurs at the position of the cathode, the loop 34 being.

coupled to the oscillating magnetic eld within the resonator which isgenerated during operation of the tube. Thus, each orV the tubularmembers 24 and 25 serves as an elongated anode ofy large size, havinglarge heat dissipating capacity and vbecause of the large size of theanode construction is facilitated and at the same time the mode .ofoscillation of the electromagnetic eld within the resonator cavity issuch that while the anode is large nevertheless high frequency can begenerated. Because of the enclosed eld undesired radiations and loss ofenergy is prevented, thereby increasing the eniciency of operation andpermitting direction of the energy to the radiator 35' with very smalllosses. n

A modification of the device shown in Figures 1 and 2 is shown inFigures 5 and 6. In this modication the resonator takes the form of anelongated box-like structure. Y

The envelopell .is providedwith the usual press 4l and base d2 and pins43. The amount includes the cathode larnent 4 connected to and supportedby the leads and support wires 45 and 46, these leads extending throughthe insulating separator 4T. A pair of leads and support wires 48 and 49support the resonator 5B which encloses the cathode and is an elongatedbox-like structure. The coupling loop I within the cavity extends intothe outer tubular member 52 and `forms therewith a coaxial line andtermihates in a radiator 52. The magnets 53 and 54 supply the necessarymagnetic held preferably nearly parallel to. `the cathode. A shield 55supportedby the cavity supports may be utilized to prevent deposition ofvaporized metal on the insulating spacer 47. The operation of thisstructure is similar to that shown in Figures 1 and 2.

While I have indicated the preferred embodiments of my invention ofwhich I am now aware and have also indicated only one specic applicationfor which my invention may be employed,

it will be apparent that my invention is by noV means limited to theexact forms illustrated or the use indicated, but that many variationsmay be made in the particular structure used and the purpose for whichit is employed without departing from the scope of my invention as setforth in the appended claims.

What I claim as new is:

1. An electron discharge device including an anode comprising a singlecavity resonator enclosing a space and resonant to electromagneticradiation at the frequency to be generated, a cathode within said anodefor supplying electrons within said space and in a region in which anoscillating electric field can exist, and means adjacent said cathodeior providing a iixed magnetic iield within said anode and between saidvcathode and said anode and to which said electrons are subjected.

and within said cavity resonator to which said electrons are subjected,and means coupled to said resonator for coupling to the oscillatingelectromagnetic iield Vwithin said cavity resonator and including a Waveguide constituting a radiator.

3. An electron discharge device having a cavity resonator including apair of coaxial tubular members coextensive with each other, saidtubular members having both ends closed, a cathode positioned betweenand out of contact with said tubular members and parallel to thelongitudinal axis of said 'tubular members and means adjacent saidcathode for providing an electromagnetic eld between said cathode andsaid tubular members and a coupling means extending Within said cavityresonator and terminating in a coaxial line, said coaxial line includingan inner conductor and outer conductor, said inner conductor extendingbeyond the end of said outer conductor and providing a radiator for saidelectron discharge device.

4. An electron discharge device including an anode comprising a cavityresonator enclosing an annular-like space and resonant toelectromagnetic radiation at Vthe frequency to be generated, a cathodeonly within said anode and out of Contact with the walls thereof forsupplying electrons within said space in a region in which anoscillating electric iield can exist, and a means adjacent said cathodefor providing a magnetic eld between said cathode and said anode andWithin said cavity resonator to which said electrons are subjected.

5. An electron discharge device including an elongated cathode, a cavityresonator enclosing said cathode, a transverse section of the walls ofthe said cavity resonator bounding a rectangular-shaped area, saidcathode lying parallel to the longest; side of said area and between andout of contact wtih the walls of the cavity resonator, said cathodebeing the only electrode within said resonator, said walls providing ananode for said electron discharge device and means adjacent said cathodefor providing a magnetic iield between said cathode and the walls ofsaid cavity resonator, a coaxial line coupled to the space within thecavity resonator and including an outer conductor and inner conductor,said inner conductor extending beyond the end of said outer conductorand providing a radiator.

6. An electron discharge device including a 1invear cathode, a singlecavity resonator enclosing onlysaid cathode, the space enclosed by saidcavity resonator having a geometrically shaped transverse Section,nsaidcavity resonator having a dimension along said cathode no greater thansaid cathode, the walls of .said resonator` providing the anode of saidelectrony discharge device, and means adjacent said cathode forproviding a fixed magnetic field between said cathode ,and the walls ofsaid cavity resonator.

7. An electron discharge device including a cathode, a cavity resonatorenclosing only said cathode, the space enclosed by said cavity resonatorhaving a rectangularly shaped transverse section, said cathode lyingparallel to opposite walls of said cavity resonator and means adjacentsaid cathode for providing a magnetic field between said cathode and thewalls of said cavity resonator.

8. An electron discharge device including an elongated cathode, a cavityresonator enclosing only said cathode, the space enclosed by said cavityresonator having a rectangularly shaped transverse section, said cathodebeing positioned within said cavity resonator to lie transverse to theelectric eld within said cavity resonator and means adjacent saidcathode for providing an electromagnetic eld nearly parallel to saidcathode and between said cathode and the walls of said cavity resonator.

9. An electron discharge device having a cavity resonator and includinga pair of coaxial tubular members coextensive with each other and closedat both their ends, a cathode positioned between and out of contact withsaid tubular members and parallel to the longitudinal axis of saidtubular members, and means adjacent said cathode for providing anelectromagnetic iield between said cathode and said tubular members, anda coupling means extending within said cavity resonator and terminatingin a coaxial line.

10. An electron discharge device having an envelope containing a cavityresonator said resonator including a pair of coaxial tubular memberscoextensive with each other and closed at both their ends, a cathodepositioned between and out of contact with said coaxial tubular membersand parallel to the longitudinal axis of said tubular members, and meansadjacent said cathode for providing an electromagnetic eld between saidcathode and said tubular members, and a coupling loop extending withinsaid cavity resonator and terminating in a coaxial line, said envelopebeing provided with an elongated tubular extension, said coaxial lineextending within said extension, said coaxial line having an innerconductor and an outer conductor, said inner conductor extending beyondthe end of the outer conductor and constituting a radiator.

l1. An electron discharge device including an elongated cathode, acavity resonator enclosing only said cathode, the transverse section ofthe walls of said cavity resonator bounding a rectangularly shaped area,said cathode lying parallel to the longest side of the area and betweenand out of contact with the walls of the cavity resonator, said wallsproviding an anode for said electron discharge device, and meansadjacent said cathode for providing a magnetic eld substantiallyparallel to said cathode and between said cathode and the walls of saidcavity resonator.

12. An electron discharge device having a cavity resonator and includinga pair of coaxial tubular members coextensive with each other and closedat both their ends, a cathode positioned between and out of contact withsaid tubular members and parallel to the longitudinal axis of saidtubular members, and means adjacent said cathode for providinganelectromagnetic iield between said cathode and said tubular members.

13. An electron discharge device having a cavity resonator and includinga pair of coaxial tubular members coextensive with each other and closedat both their ends, a cathode positioned between and out of contact withsaid tubular members and parallel to the longitudinal 'axis of saidtubular members, and means adjacent said cathode for providing anelectromagnetic eld between said cathode and said tubular members, and acoupling means extending within said cavity resonator for extractingenergy from said cavity resonator.

HENRY B. DE VORE.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,295,315 Woll Sept. 8, 19422,284,751 Linder June 2, 1942 2,079,248 Fritz May 4, 1937 2,163,589Dallenbach et al. June 27, 1939 2,108,900 Peterson Feb. 22, 19382,115,521 Fritz Apr. 26, 1938 2,128,235 Dallenbach Aug. 30, 19382,063,342 Samuel Dec. 8, 1936 2,348,986 Linder May 16, 1944 2,129,713Southworth Sept. 13, 1938

